Nesoryzomys indefessus, a related extinct species, was found on Indefatigable Island. Some consider the two to be subspecies of one species, in which the Fernandina form would be Nesoryzomys indefessus narboroughi;[1] however, N. narboroughi is now considered distinct.[2]
^Dowler, R. C. 2015. Genus Nesoryzomys Heller, 1904. In: Patton, J.L., Pardiñas, U.F.J. and D'Elía, G. (eds), Mammals of South America, pp. 390-393. University of Chicago Press.